CN1178048C - Coriolis Mass Flow/Density Meter - Google Patents

Abstract

The Coriolis mass flow meter/density meter of the present invention is a compact Coriolis mass flow meter/density meter that provides highly accurate measurement results independent of the velocity field of the medium being measured. The mass flow meter/density meter includes at least one measuring tube (11) through which the medium flows, and which vibrates during operation. A measuring device (141) for measuring this vibration is disposed at the inlet end of the measuring tube (11) and provides a measurement signal ( _xs1 ). A measuring device (142) for measuring this vibration is disposed at the outlet end of the measuring tube (11) and provides a measurement signal ( _xs2 ).

Description

Coriolis Mass Flow/Density Meter

The present invention relates to Coriolis mass flow/density meters for media flowing through pipes, and to methods of producing measurements representative of mass flow rates.

In a Coriolis mass flow/density meter for a medium flowing through a pipe, the measurement of the mass flow rate causes the medium to flow through a flow tube inserted into the pipe, vibrating during operation so that the medium is subjected to Coriolis Based on the principle of Ollie force. Coriolis forces cause the inlet and outlet end portions of the flow tube to vibrate out of phase with respect to each other. The magnitude of these differences is a measure of mass flow rate. Then, the vibration of the flow tube is detected by two vibration sensors placed at a given distance from each other along the flow tube, and converted into measurement signals by these sensors, and the mass flow rate is obtained according to the phase difference of these measurement signals.

US Patent 4187721 discloses a Coriolis mass flow meter comprising:

- A single U-shaped flow tube with inlet and outlet ports through which the medium flows during operation;

- support means fixed on the inlet and outlet ends of the flow tube so that the flow tube can be vibrated;

- vibrators for vibrating the flow tubes during operation;

- a first measurement device arranged at the inlet end of the flow tube for measuring vibrations during operation and outputting a first measurement signal;

- a second measurement device arranged at the outlet end of the flow tube for measuring vibration during operation and outputting a second measurement signal; and

- Evaluation electronics for outputting, during operation, a first measured value representing a mass flow rate, the mass flow rate being derived from the first and the second measured signal.

In addition, EP-A 849568 (corresponding to U.S. serial number 08/940644, application date September 30, 1997) discloses a Coriolis mass flowmeter, including:

- a single straight-through flow tube with inlet and outlet ports through which the medium flows during operation;

- a support device fixed on the inlet and outlet ends of the flow tube so that the flow tube can be vibrated;

- vibrators for vibrating the flow tubes during operation;

- a first measurement device arranged at the inlet end of the flow tube for measuring vibrations during operation and outputting a first measurement signal;

- a second measurement device arranged at the outlet end of the flow tube for measuring vibration during operation and outputting a second measurement signal; and

- Evaluation electronics for outputting, during operation, a measured value representative of the mass flow rate derived from the first and second measurement signal.

In addition, US Patent 4660421 and US Patent 4733569 both disclose a Coriolis mass flowmeter, including:

- a helical flow tube with inlet and outlet ports through which the medium flows during operation;

- a support device fixed on the inlet and outlet ends of the flow tube so that the flow tube can be vibrated;

- vibrators for vibrating the flow tubes during operation;

- a first measurement device arranged at the inlet end of the flow tube for measuring vibrations during operation and outputting a first measurement signal;

- a second measurement device arranged at the outlet end of the flow tube for measuring vibration during operation and outputting a second measurement signal; and

- During operation, evaluation electronics for outputting a measured value representative of the mass flow rate, which is derived from the first and second measurement signal.

Furthermore, US Patent 4491025, US Patent 4660421 and US Patent 5218873 all disclose a Coriolis mass flow meter having two communicating flow tubes through which a medium flows during operation. The flow tubes are interconnected by an inlet first manifold having an inlet first end and an outlet second manifold having an outlet second end and are secured by support means so that the flow tubes can be vibrated.

US Patent 4187721 mentioned at the outset and EP-A849568 mentioning a Coriolis mass flow meter can also be used to measure the instantaneous density of a flowing medium. For the present invention it is then assumed that the device referred to above as a Coriolis mass flow meter also measures the instantaneous density of the flowing medium, even though this is generally not stated in the respective documents, since this is self-evident.

In the case of the Coriolis mass flowmeter and the Coriolis mass flow/density meter, the ratio of the width D of the flow tube to the length of the flow tube (D/L ratio) is very important for measurement accuracy. If a single flow tube is used, the width D is substantially equal to the nominal diameter of the tube.

At D/L ratios greater than about 0.05, the instantaneous flow velocity field of the medium in the flow tube affects the measurement accuracy, so that the resulting increased measurement error is no longer negligible. Measurements have shown that at D/L ratios greater than 0.05, this effect of the velocity field may result in an additional error of a few thousandths to one percent.

However, due to constraints on the design of Coriolis mass flow/density meters, i.e., on the one hand, by the nominal pipe diameter specified in the specific application, on the other hand, by requiring the Coriolis mass flow/density meter to be as large as possible The fact that it is short and compact limits the minimization of the D/L ratio.

It is an object of the present invention to provide a Coriolis mass flow/density meter which provides highly accurate measurements independent of the instantaneous flow velocity field while being as compact as possible in construction . Another object of the invention is to provide a method for producing such measurements.

In order to achieve the purpose of the first invention above, the present invention provides a Coriolis mass flow/density meter for a medium flowing through a pipeline, the Coriolis mass flow/density meter comprising:

- at least one flow tube having an inlet port and an outlet port through which a medium flows during operation;

- support means fixed on the inlet and outlet ends of the flow tube so that the flow tube can be vibrated;

- vibrators for vibrating the flow tubes during operation;

- a first measurement device arranged at the inlet end of the flow tube for measuring vibrations during operation and outputting a first measurement signal;

- a second measuring device arranged at the outlet end of the flow tube for measuring vibrations during operation and outputting a second measurement signal;

- during operation, a third measuring device outputting a third measuring signal representative of the instantaneous Reynolds coefficient of the flowing medium; and

-Evaluation electronics for, during operation, the output

-- a first measurement representing the mass flow rate, the first measurement being derived from the first, second and third measurement signals, and

- A second measured value representing the instantaneous density of the medium, which is derived from the first and the second measured signal.

Additionally, the present invention includes a method of producing a first measurement representative of mass flow rate with a Coriolis mass flow/density meter for a medium flowing through a pipeline, said Coriolis mass flow/density meter comprising:

- at least one flow tube having an inlet port and an outlet port through which a medium flows during operation;

- support means fixed on the inlet and outlet ends of the flow tube so that the flow tube can be vibrated;

- vibrators for vibrating the flow tubes during operation;

The method comprises the steps of:

- detecting the vibration of the flow tube and generating a first measurement signal representative of the vibration at the inlet end and a second measurement signal representative of the vibration at the outlet end for forming an intermediate value representative of the uncorrected mass flow rate;

- generating a third measurement signal representative of the Reynolds coefficient of the flowing medium using the intermediate value and using a fourth measurement signal representative of the dynamic viscosity of the medium; and

- Correction of the intermediate value using the correction value derived from the third measurement signal.

In a first embodiment of the Coriolis mass flow/density meter according to the invention, the evaluation electronics provide a correction value originating from the third measurement signal.

In a second embodiment of the Coriolis mass flow/density meter according to the invention, a constant correction value for laminar flow determined by calibration is used, a constant correction value for turbulent flow determined by calibration is used, and a value determined according to an interpolation function is used. , an interpolated correction value between these two constant correction values, the evaluation electronics provide the correction value.

In a third embodiment of the Coriolis mass flow/density meter according to the invention, the evaluation electronics comprise a table memory in which digitized correction values dependent on the Reynolds coefficient are stored, by means of the third measurement A digital memory access address formed by the signal, the table memory provides correction values.

In a fourth embodiment of the Coriolis mass flow/density meter according to the invention, the evaluation electronics provide an intermediate value derived from the first and second measurement signal, the intermediate value representing the uncorrected mass flow rate.

In a fifth embodiment of the Coriolis mass flow/density meter according to the invention, the evaluation electronics output the first measured value responsive to the intermediate value and the correction value.

In a sixth embodiment of the Coriolis mass flow/density meter according to the invention, the Coriolis mass flow/density meter comprises a fourth measuring device which measures the dynamic viscosity of the medium and outputs an output representative of said The fourth measurement signal of dynamic viscosity.

In a seventh embodiment of the Coriolis mass flow/density meter according to the invention, the third measurement means outputs a third measurement signal in response to the uncorrected intermediate value and the fourth measurement signal.

In an eighth embodiment of the Coriolis mass flow/density meter according to the invention, the fourth measuring means measures the kinematic viscosity of the medium and outputs a fifth measurement signal representative of said kinematic viscosity.

In a ninth embodiment of the Coriolis mass flow/density meter according to the invention, the fourth measurement means outputs a fourth measurement signal in response to the second measurement value and the fifth measurement signal.

In a tenth embodiment of the Coriolis mass flow/density meter according to the invention, the exciter comprises a coil supplied with excitation energy, and from the current and/or voltage of the coil the fourth measuring means derives the first A fourth measurement signal and/or a fifth measurement signal.

In an eleventh embodiment of the Coriolis mass flow/density meter according to the invention, the fourth measuring means derives the fourth and/or fifth measurement signal from the pressure difference measured along the pipeline.

In a first embodiment of the method according to the invention, a fourth measurement signal is derived as a function of the current and/or voltage of the excitation energy supplied to the oscillator.

In a second embodiment of the method according to the invention, a fourth measurement signal is obtained from a pressure difference measured along the pipeline.

One of the advantages of the present invention is that even at D/L ratios greater than 0.05, Coriolis mass flow/density meters provide mass flow rates in which the effects of the instantaneous flow field on measurement accuracy have been compensated for.

The present invention will become apparent according to the following description of the embodiments in conjunction with the accompanying drawings. In the drawings, the same components are denoted by the same reference numerals; already introduced reference characters are omitted in subsequent drawings for the sake of clarity. in:

Figure 1 is a vertical longitudinal view of a mass flow sensor of a Coriolis mass flow/density meter, partly shown in cross-section.

Figure 2 is a schematic block diagram of subcircuits of the evaluation electronics of a Coriolis mass flow/density meter for increased measurement accuracy;

3 is a schematic block diagram of subcircuits for deriving mass flow values with sufficient accuracy from uncorrected mass flow values using corrected values;

Fig. 4 is a schematic block diagram of a sub-circuit for obtaining a mass flow correction value according to a measured Reynolds coefficient;

Fig. 5 is a schematic block diagram of a subcircuit for generating a mass flow correction value according to an interpolation function;

Fig. 6a is a schematic block diagram of a sub-circuit for determining the Reynolds coefficient according to the measured dynamic viscosity of the medium;

Fig. 6b is a schematic block diagram of a sub-circuit for determining the Reynolds coefficient according to the measured kinematic viscosity of the medium;

Fig. 7 is a schematic block diagram of a sub-circuit for determining the kinematic viscosity of the medium according to the measured excitation energy of the vibrator;

Fig. 8 a is the schematic block diagram of the sub-circuit for obtaining the measured value of the kinematic viscosity under the condition of laminar flow according to the pressure difference measured along the flow direction;

Fig. 8b is a schematic block diagram of a sub-circuit for obtaining a measured value of kinematic viscosity under turbulent flow based on the pressure difference measured along the direction of flow; and

Figure 9 is a schematic block diagram of a subcircuit for determining the instantaneous kinematic viscosity of a medium.

Referring now to FIG. 1, FIG. 1 shows a vertical longitudinal view, partly in cross-section, of a mass flow sensor 1 of a Coriolis mass flow/density meter having a single straight-through flow tube 11 having an inlet end first end and outlet end second end.

The first end of the flow tube 11 is provided with a first flange 111 and the second end is provided with a second flange 112, so that the mass flow sensor 1 can be inserted into the pipeline through which the medium flows during operation in a pressure-tight manner.

The mass flow sensor 1 also includes a supporting device 12, the supporting device 12 has a first end plate 121 fixed on the first end of the flow tube 11, a second end plate 122 fixed on the second end of the flow tube 11, and an insert Support tube 123 between first and second end plates 121 , 122 . End plates 121 , 122 are connected to flow tube 11 in a rigid and pressure-tight manner, in particular vacuum-tight manner. The flow tube 11 is thus mounted in a self-supporting manner within the lumen of the support tube 123 between the end plates 121, 122, thereby allowing it to vibrate.

The joints between flow tube 11 and end plates 121, 122 and flanges 111, 112, and the joints between end plates 121, 122 and support tube 123 may be, for example, welded joints or welded seams; end plate 121 , 122 can also be fixed on the support tube 123 by means of screws, one of which screw 124 is shown in FIG. 1 . It is also possible to form the two end plates 121 , 122 integrally with the support tube 123 .

In addition to mass flow sensors of the type shown in Figure 1, mass flow sensors with two straight-through flow tubes are also commonly used.

But instead of straight-through flow tubes all other forms of flow tubes described for Coriolis mass flow/density meters can be used, especially U-shaped or omega-shaped or helical flow tubes. Two or more flow tubes, preferably two flow tubes, may be connected in parallel or in series with respect to the flow of the medium. If flow tubes are connected in parallel, the ends are fitted with appropriate manifolds to separate and mix the flowing media.

The medium can be any fluid substance, especially liquid, gas or vapour.

Flow tubes are preferably made of titanium, zirconium or high-quality steel.

Fig. 1 also shows the vibrator 13, between the flow tube 11 and the support tube 123, preferably in the middle position between the first and second end plates 121, 122, the vibrator 13 is arranged on the support device 12 Inside. In operation, the exciter 13 causes the flow tube 11 to vibrate at a mechanical resonant frequency, which itself is a measure of the instantaneous density of the medium.

The exciter 13 can be, for example, a solenoid assembly comprising a soft magnetic core fixed to the flow tube 11, a permanent magnet movable in the flow tube 11, and fixed to the support tube 123 and passing through it during operation. A coil with variable excitation current. The permanent magnet is moved under the action of the time-varying excitation current, causing the flow tube 11 to vibrate, while the inlet and outlet end sections vibrate out of phase with respect to each other as media flows through the flow tube 11 .

For the excitation electronics for exciting the exciter 13, see US Patent 4,801,897.

In the case of a straight-through flow tube, the vibration is usually a bending vibration, which is not too different from that of a string. These bending vibrations may have torsional vibrations superimposed on them, see EP-A 849568. In addition to bending/torsional vibrations, hoop mode vibrations are often excited, in which case the flow tube moves in a peristaltic manner, see US Patent 4949583.

In the case of U-shaped or omega-shaped flow tubes, the vibration is a cantilever vibration which is not much different from that of a tuning fork, see US Patent 4,187,721.

A first measuring device 141 and a second measuring device 142 are arranged in the support device 12 at a given distance from each other along the flow tube 11 for measuring vibrations. The measuring devices 141, 142 are preferably located at the same distance from the middle of the flow tube 11 and provide a first measurement signal _xs1 and a second measurement signal _xs2 representative of the vibration.

To this end, the measuring means 141 , 142 comprise vibration sensors, which are preferably realized in the form of electrodynamic vibration sensors as disclosed in US patent 5736653, but can also be designed as optical vibration sensors, see US patent 4801897.

The mass flow sensor 1 is protected from environmental influences by a sensor housing 15 . The sensor housing 15 is designed to house the support device 12 and all electrical leads connected to the mass flow sensor 1, which are not shown for clarity.

The sensor housing 15 has a neck-shaped transition section 16 to which the electronics housing 17 is fastened.

In the electronics housing 17 the excitation and evaluation electronics 2 mentioned above are housed, as well as other circuits also used for the operation of the Coriolis mass flow/density meter. These circuits can be, for example, the electronics that power a Coriolis mass flow/density meter powered by an external power source, and/or transfer data between a Coriolis mass flow/density meter and an external signal processor communication electronics.

If the vibration behavior of the mass flow sensor 1 is to be adversely affected by the electronics housing 17 , the electronics housing 17 can be spaced from the mass flow sensor 1 at a certain distance. Then, there will only be electrical leads between the electronics housing 17 and the mass flow sensor 1 , so that the electronics housing 17 and the sensor 1 are practically isolated from each other with regard to vibrations.

Fig. 2 shows a block diagram of a subcircuit of the evaluation electronics 2 of the Coriolis mass flow/density meter, which subcircuit provides a first measured value x _m representative of the mass flow rate.

The measurement signals x _s1 , x _s2 are fed to the measurement circuit 21 of the evaluation electronics 2 . The measurement circuit 21 can be implemented, for example, by the evaluation electronics of a Coriolis mass flow/density meter as disclosed in US Pat. Other measurement electronics for Coriolis mass flow/density meters familiar to those skilled in the art may also be used.

However, at a large D/L ratio, the mass flow rate measured by the measuring circuit 21 is not accurate enough and needs to be corrected; therefore, the mass flow rate measured by the measuring circuit 21 is called the intermediate value X _m ^* here, according to the intermediate value X _m ^* , the measured value X _m is obtained, and the measured value X _m represents the mass flow rate with sufficient precision.

The correction of the median value X _m ^* is based on the following knowledge of the inventors.

The mass flow rate in flow tube 11 is given by:

$\frac{\mathrm{<span\; class="notranslate">\; wxya</span>}}{\mathrm{<span\; class="notranslate">\; dt</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; \&pi;</span>}}{\mathrm{<span\; class="notranslate">\; 4</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span>{\mathrm{<span\; class="notranslate">\; D.</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span>\mathrm{<span\; class="notranslate">\; \&rho;</span>}<span\; class="notranslate">\; \&Center\; Dot;</span>{\mathrm{<span\; class="notranslate">\; v</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>$

in

dQ/dt = mass flow rate

D = inner diameter of flow tube 11

ρ = instantaneous density of the medium

v _m = average velocity of the medium flowing through the flow tube 11

The average velocity v _m is the arithmetic mean of all velocity vectors of the flowing medium in the cross-section of the flow tube 11 .

The median _Xm ^* is given by

in

_Xf = measured value representing the instantaneous frequency of the vibration of the flow tube 11

X _φ = measured value representing the instantaneous phase difference between the measured signals x _s1 , x _s2

K ₁ = first parameter of Coriolis mass flow/density meter

The parameter K ₁ mainly depends on the instantaneous temperature of the medium; it also depends on the instantaneous density of the medium.

For equation (2), it is assumed that the properties of the medium that determine the parameter _K1 , that is, the instantaneous temperature and instantaneous density of the medium are known, because during the operation of the Coriolis mass flow/density meter, the instantaneous temperature and instantaneous density of the medium Also measured, see US Patent 4,768,384 for temperature measurements, and US Patent 4,187,721 for density measurements.

For equation (2), it is also assumed that the Coriolis-induced phase difference between flow tube vibrations sensed at the inlet port and flow tube vibrations sensed at the outlet port is proportional to the instantaneous mass flow rate. This assumption assumes that all flow velocity fields generated in the flow tube 11 generate the same Coriolis force at the same instantaneous flow rate. This is true with increasing precision as the D/L ratio decreases, since in this case all velocity fields are identical or at least very similar to each other. At large D/L ratios, especially at D/L ratios greater than 0.05, the validity of this assumption decreases, resulting in a median value _Xm ^* of reduced accuracy.

Studies have shown that the measurement accuracy values depend in particular on whether the medium flow is laminar or turbulent.

Thus, to determine the measured value _Xm , the intermediate value _Xm ^* can be corrected by determining the presence of laminar or turbulent flow in the flow tube 11 and taking this into account in the form of a correction value _Xk for the intermediate value _Xm ^* . Modifying equation (2) gives:

Equation (3) is implemented by the second subcircuit 22 of the evaluation electronics 2 , which is shown in block diagram form in FIG. 3 .

The sub-circuit 22 includes a first adder 221. The adder 221 generates a first sum value according to the correction value X _k at the first input terminal and the value of 1 at the second input terminal, and outputs the first sum value at the output terminal.

The subcircuit 22 also includes a first multiplier 222 having a first input for the first sum value and a second input for the intermediate value _Xm ^* . The multiplier 222 provides at output a first multiplied value (1+X _K )·X _m ^* , which corresponds to the measured value X _m .

In the present invention, X _k is derived from the instantaneous Reynolds coefficient of the medium, and describes the value of the velocity field of the flowing medium. The mass flow sensor 1 then comprises a third measuring device 143 for measuring the instantaneous Reynolds coefficient of the medium, see FIG. 2 . Measuring device 143 provides a third measurement signal x _Re representing the Reynolds coefficient and feeds it to evaluation electronics 2 .

In _the case of laminar flow, the value of the measurement signal x _Re is smaller than in the case of turbulent flow. Thus, for each width D of the flow tube 11, and the associated nominal width of the pipe, there is an upper limit for the Reynolds coefficient for laminar flow and a lower limit for the Reynolds number for turbulent flow, which are different. These two limit values are determined during calibration.

The upper limit value of the Reynolds coefficient of the laminar flow determined during the calibration is represented by a second parameter K ₂ which is stored in the evaluation electronics 2 . The lower limit value of the Reynolds coefficient of the turbulent flow determined during the calibration is represented by a third parameter K ₃ which is stored in the evaluation electronics 2 .

A comparison of the measurement signal x _Re with these two parameters K ₂ , K ₃ indicates whether laminar or turbulent flow is present in the flow tube 11 and provides a corresponding correction value X _K . The comparison is based on the following inequality:

in

X _K2 = constant correction value for laminar flow, determined by calibration

X _K3 = constant correction value for turbulence, determined by calibration

f(x _Re ) = interpolation function monotonically rising from X _K2 to X _K3 , whose shape can be adjusted, see below.

The result of the comparison of the measured signal x _Re with these two parameters K ₂ , K ₃ according to equation (4) is the corrected value X _K =X _K2 for laminar flow and X _K =X _K3 for turbulent flow, or corresponds to The interpolation correction value X _K =f(x _Re ) of the interpolation function f(x _Re ).

Equation (4) is implemented by the third sub-circuit 23 , the individual functional elements of which are represented in block diagram form in FIG. 4 .

The subcircuit 23 comprises a first comparator 231 having a reference input for the parameter K ₂ and a signal input for the measurement signal x _Re . The comparator 231 provides a first binary value for x _Re < K ₂ , which is 1 when the instantaneous value of the measurement signal x _Re is smaller than the value of the parameter K ₂ ; otherwise, the first binary value is 0. This first binary value is supplied to a first input of a second multiplier 232 . A second input of the second multiplier 232 receives a constant correction value X _K2 for laminar flow.

The subcircuit 23 also comprises a second comparator 233 having a reference input for the parameter K ₃ and a signal input for the measurement signal x _Re . The comparator 233 provides a second binary value for x _Re > K ₃ , which is 1 when the instantaneous value of the measurement signal x _Re is greater than the value of the parameter K ₃ ; otherwise, the second binary value is 0.

This second binary value is supplied to a first input of a third multiplier 234 . A second input of the third multiplier 234 receives a constant correction value X _K3 for turbulence.

The subcircuit 23 also includes a NOR gate 235 having a first input for a first binary value and a second input for a second binary value. NOR gate 235 provides a third binary value for K ₂ ≤ x _Re ≤ K ₃ , when the second and second binary values are 0, the third binary value is 1; otherwise the third binary value The value is 0.

An inverter 236 following the NOR gate 235 changes the third binary value to an inverted fourth binary value which is applied to the third input of the second multiplier 232, and Applied to the third input terminal of the multiplier 234 .

Thus, the multiplier 232 provides a second product value equal to the constant correction value X _K2 for laminar flow if the first and fourth binary values are 1; otherwise the second product value is zero. Similarly, multiplier 234 provides a third product value equal to the constant correction value X _K3 for turbulence if the second and fourth binary values are 1; otherwise, the third product value is zero.

An interpolation correction value corresponding to the interpolation function f(x _Re ) (the generation of which will be explained below) is supplied to a first input terminal of the fourth multiplier 237 . The third binary value is provided to the second input terminal of the multiplier 237, thereby the multiplier 237 provides the fourth product value, if the third binary value is 1, then the fourth product value is equal to the value corresponding to f(x _Re ) interpolation correction value; if the third binary value is 0, then the fourth product value is also 0.

The second, third and fourth product values are supplied to the first, second and third input terminals of the second adder 238, respectively, and the second adder 238 outputs the second sum value. Since only the second or third or fourth product value is non-zero at any given time, the second sum value corresponds to the desired correction value X _K .

The correction value X _K can also be generated using a fuzzy logic circuit configured in the sub-circuit 23 . To achieve this, the first comparator 231 is replaced by a first membership function for laminar flow, the second comparator 233 by a second membership function for turbulent flow, and a third membership function for coexisting laminar and turbulent flow NOR gate 235. These membership functions have to be determined from calibration measurements and provide first, second and third membership values that lie between 0 and 1 instead of the first, second and third binary values, respectively. The inverter 236 has to be replaced by, for example, a subtractor which then subtracts the third membership value from the value one.

For flow conditions with laminar and turbulent components, the correction value XK is interpolated according to equation (4) using the interpolation function f(x _Re ). The interpolation function f(x _Re ) can be expanded in the form of a power series in a conventional manner, for example with the parameter _K as the center, so that

$\mathrm{<span\; class="notranslate">\; f</span>}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; Re</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\underset{\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 0</span>}}{\overset{<span\; class="notranslate">\; \&infin;</span>}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}{\mathrm{<span\; class="notranslate">\; a</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}{<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; Re</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; K</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; no</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; a</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; a</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; Re</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; K</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; a</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}{<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; Re</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; K</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 5</span>}<span\; class="notranslate">\; )</span>$

Thus, by using an approximate polynomial of degree n, the interpolation function f(x _Re ) can be realized with arbitrary precision. The coefficients a _n of the interpolation function f(x _Re ) must be determined by calibration.

For example, if the approximating polynomial is only a polynomial of degree one, i.e. if n=1, for the corresponding interpolation function f(x _Re ), the linear relation is obtained:

f ₁ (x _Re ) = α ₀ +α ₁ (x _Re -K ₂ ) (6)

Using equation (4),

${\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; Re</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="x\; K"\; filenames="C9980291100283.png"\; state="\{\{state\}\}">x</figure-callout></span><figure-callout\; id="2"\; label="x\; K"\; filenames="C9980291100283.png"\; state="\{\{state\}\}">\; </figure-callout>}}_{\mathrm{<span\; class="notranslate">\; </span>}}<span\; class="notranslate">\; +</span>\frac{{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; K</span>}\mathrm{<span\; class="notranslate">\; 3</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; K</span>}\mathrm{<span\; class="notranslate">\; 2</span>}}}{{\mathrm{<span\; class="notranslate">\; K</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; K</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; Re</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; K</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 7</span>}<span\; class="notranslate">\; )</span>$

FIG. 5 shows a block diagram of a fourth subcircuit 24, which implements the interpolation function f(x _Re ) according to equation (7).

The subcircuit 24 includes a first subtractor 241 having a subtrahend input for a correction value X _K2 for laminar flow and a subtrahend input terminal for a correction value X _K3 for turbulent flow, the first subtractor 241 providing information on X _K2 − The first difference of X _K3 . A second subtractor 242 having a subtrahend input for the parameter K ₂ and a minuend input for the parameter K ₃ provides a second difference with respect to K ₃ −K ₂ . A third subtractor 243 having a subtrahend input for the parameter K ₂ and a minuend input for the measurement signal x _Re provides a third difference with respect to x _Re −K ₂ .

Subcircuit 24 also includes a first divider 244 having a dividend input for the first difference value and a divisor input for the second difference value. The divider 244 outputs a first quotient corresponding to the expression (X _K3 -X _K2 )/(K ₂ -K ₃ ).

A fifth multiplier 245 having a first input for the first quotient and a second input for the third difference generates a relation (x _Re −K ₂ )·(X _K3 −X _K2 )/(K ₂ -K ₃ ), the fifth product value is supplied to a first input of the third adder 246 . _The correction value X _K2 of _the laminar _flow is provided to _the second input terminal _of the _{adder 246} , so that the adder 246 provides ) of the third sum. If K ₂ ≤ x _Re ≤ K ₃ , ie under flow conditions with laminar and turbulent components, then this third sum corresponds to the required interpolated correction value X _K =f(x _Re ).

Instead of equation (7), any other approximation polynomial based on equations (4) and (5) can be implemented using subcircuit 24 .

Instead of the subcircuits 23 and 24 respectively shown in FIGS. 4 and 5 , the evaluation electronics 2 may comprise a table memory containing discrete values for the correction value X _K . These discrete values can be accessed via digital memory addresses derived from the measurement signal x _Re . This digital memory address is formed by an analog-to-digital converter following the encoder. The table memory may be a programmable read-only memory, such as EPROM or EEPROM.

For the measurement of the Reynolds number necessary according to equation (4), the following relationship is used:

$\mathrm{<span\; class="notranslate">\; Re</span>}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; \&eta;</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span>\frac{\mathrm{<span\; class="notranslate">\; 4</span>}}{\mathrm{<span\; class="notranslate">\; \&pi;</span>}<span\; class="notranslate">\; \&Center\; Dot;</span>\mathrm{<span\; class="notranslate">\; D.</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span>\frac{\mathrm{<span\; class="notranslate">\; wxya</span>}}{\mathrm{<span\; class="notranslate">\; dt</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; \&zeta;</span>}<span\; class="notranslate">\; \&Center\; Dot;</span>\mathrm{<span\; class="notranslate">\; \&rho;</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span>\frac{\mathrm{<span\; class="notranslate">\; 4</span>}}{\mathrm{<span\; class="notranslate">\; \&pi;</span>}<span\; class="notranslate">\; \&Center\; Dot;</span>\mathrm{<span\; class="notranslate">\; D.</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span>\frac{\mathrm{<span\; class="notranslate">\; wxya</span>}}{\mathrm{<span\; class="notranslate">\; dt</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 8</span>}<span\; class="notranslate">\; )</span>$

in

η = dynamic viscosity of medium

ζ = kinematic viscosity of the medium

Substituting the average velocity v _m from equation (1) into equation (8) gives the following Reynolds coefficient

$\mathrm{<span\; class="notranslate">\; Re</span>}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; \&eta;</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span>\frac{\mathrm{<span\; class="notranslate">\; 4</span>}}{\mathrm{<span\; class="notranslate">\; \&pi;</span>}<span\; class="notranslate">\; \&Center\; Dot;</span>\mathrm{<span\; class="notranslate">\; D.</span>}}<span\; class="notranslate">\; \&CenterDot;</span>\frac{\mathrm{<span\; class="notranslate">\; wxya</span>}}{\mathrm{<span\; class="notranslate">\; dt</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; \&zeta;</span>}<span\; class="notranslate">\; \&CenterDot;</span>\mathrm{<span\; class="notranslate">\; \&rho;</span>}}<span\; class="notranslate">\; \&CenterDot;</span>\frac{\mathrm{<span\; class="notranslate">\; 4</span>}}{\mathrm{<span\; class="notranslate">\; \&pi;</span>}<span\; class="notranslate">\; \&CenterDot;</span>\mathrm{<span\; class="notranslate">\; D.</span>}}<span\; class="notranslate">\; \&CenterDot;</span>\frac{\mathrm{<span\; class="notranslate">\; wxya</span>}}{\mathrm{<span\; class="notranslate">\; dt</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 9</span>}<span\; class="notranslate">\; )</span>$

According to the invention, according to equation (9), the dynamic or kinematic viscosity of the medium is used to generate the third measurement signal x _Re and thus to determine the correction value X _K , since the instantaneous density ρ of the medium can be taken into account, easily Convert these two viscosities into each other.

If dynamic viscosity is used, substituting the corresponding measured signal into equation (9) gives the following relationship for the measured signal x _Re :

${\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; Re</span>}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; K</span>}}_{\mathrm{<span\; class="notranslate">\; 4</span>}}}{{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; \&eta;</span>}}}<span\; class="notranslate">\; \&CenterDot;</span>{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}}^{<span\; class="notranslate">\; *</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 10</span>}<span\; class="notranslate">\; )</span>$

in

x _η = fourth measurement signal representing the dynamic viscosity of the medium

K ₄ = fourth parameter derived from the quotient 4/πD

Equation (10) is implemented in a third measuring device 143 having a fifth sub-circuit 25, which is represented in block diagram form in FIG. 6a.

The subcircuit 25 comprises a second divider 251 having a dividend input for the parameter _K4 and a divisor input for the measurement signal _xn . The divider 251 outputs a second quotient with respect to K ₄ /x _η , which is fed to a first input of a sixth multiplier 252 . The intermediate value X _m ^* is supplied to a second input of the multiplier 252 . Thus, the multiplier 252 provides a sixth product value corresponding to the measurement signal _xRe according to equation (10).

The measurement signal _xn necessary to determine the measurement signal _xRe according to equation (10) is generated by a further, fourth measurement device 144, see FIG.

According to equation (8), the kinematic viscosity and the instantaneous density of the medium can be used to determine the dynamic viscosity of the medium. Using equation (9), the following measurement signal x _η is given

x _η = x _ζ · X _ρ (11)

in

x _ζ = fifth measurement signal representing the kinematic viscosity of the medium

X _ρ = second measurement representing the instantaneous density of the medium.

In an embodiment of the invention based on equation (11), the measurement device 144 uses the measurement signal x _ζ representative of the kinematic viscosity of the medium to generate the measurement signal x _η . Thus, the subcircuit 25 represented in block diagram form in Fig. 6b comprises a seventh multiplier 253 having a first input for the measurement signal _xζ and a second input for the measurement value _Xp . The _multiplier 253 outputs a measurement signal x _η in the form of a product value, which is supplied to the divisor input of the second divider 251 . The measured value _Xp is derived from, for example, the instantaneous vibration frequency of the flow tube, see US patent 4187721 mentioned above.

The measurements necessary to generate the measurement signal x _ζ will be described below. Since the viscosity is a value describing the internal friction of the flowing medium, the inventors concluded that by measuring the excitation energy supplied to the vibrator 13, the kinematic viscosity can be determined. When compared to an empty flow tube 11, the vibration of the diverter flow tube 11 is further attenuated as a function of the viscosity of the medium, especially the kinematic viscosity, due to the internal friction of the medium. In order to maintain the vibration of the flow tube 11, the additional energy loss due to friction must be compensated by correspondingly increasing the excitation energy.

Thus, in a preferred embodiment of the invention, the measurement signal x _ζ is determined using the following relation:

x _ζ =K ₅ ·(x _exc -K ₆ ) ² (12)

in

x _exc = sixth measurement signal representing the excitation energy supplied to the vibrator 13

K ₅ , K ₆ = the fifth constant parameter and the sixth constant parameter, respectively.

According to equations (11) and (12), the measurement signal xζ depends only on defined quantities produced in the operation of the Coriolis mass flow/density meter, i.e. on the measured value _Xp and on Measure signal x _exc .

In an embodiment of the invention based on equation (12), the measurement device 144 includes a sixth subcircuit 26, which is represented in block diagram form in FIG.

The subcircuit 26 comprises a fourth subtractor 261 having a subtrahend input for the measurement signal x _exc representing the excitation energy and a subtrahend input for the parameter K ₆ . The subtractor 261 generates a fourth difference value for x _exc −K ₆ and supplies it to the signal input of the first exponentiator 262 . A value of 2 is provided to the exponentiation input so that the exponentiator 262 changes the fourth difference value to the first exponent value with respect to (x _exc −K ₆ ) ² . _This power value is fed to the first _input terminal of the eighth multiplier 263, _and the eighth multiplier 263 multiplies the power value by the parameter K ₅ provided at the second input terminal to form ) ² 's eighth product value, which corresponds to the measured signal x _ζ .

The measurement signal x _exc representing the excitation energy is generated by a current and/or voltage measurement at the shaker, or by an impedance measurement. In one embodiment of the invention, the voltage-to-current converter associated with the vibrator 13 formed by the solenoid assembly converts the excitation voltage applied to the coil into a current proportional to the voltage, which is then supplied by a subsequent The rms converter converts to rms values. The root mean square value is then the measurement signal representing the excitation energy x _exc .

Instead of measuring the excitation energy, another possibility for determining the kinematic viscosity of the medium is to measure and calculate the pressure difference along the pipe or along a suitable measuring length of the flow tube 11 .

In the case where laminar flow dominates along this measurement length, the kinematic viscosity is:

$\mathrm{<span\; class="notranslate">\; \&zeta;</span>}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; \&pi;</span>}<span\; class="notranslate">\; \&Center\; Dot;</span>{\mathrm{<span\; class="notranslate">\; D.</span>}}^{\mathrm{<span\; class="notranslate">\; 4</span>}}}{\mathrm{<span\; class="notranslate">\; L</span>}}<span\; class="notranslate">\; \&CenterDot;</span>{<span\; class="notranslate">\; (</span>\frac{\mathrm{<span\; class="notranslate">\; wxya</span>}}{\mathrm{<span\; class="notranslate">\; dt</span>}}<span\; class="notranslate">\; )</span>}^{<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; \&CenterDot;</span>\mathrm{<span\; class="notranslate">\; \&Delta;p</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 13</span>}<span\; class="notranslate">\; )</span>$

In cases where turbulent flow dominates, the kinematic viscosity is (Δp) ⁴

$\mathrm{<span\; class="notranslate">\; v</span>}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; 0,3</span>}}^{<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 4</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span>\frac{{\mathrm{<span\; class="notranslate">\; D.</span>}}^{\mathrm{<span\; class="notranslate">\; 19</span>}}}{{\mathrm{<span\; class="notranslate">\; L</span>}}^{\mathrm{<span\; class="notranslate">\; 4</span>}}}<span\; class="notranslate">\; \&CenterDot;</span>{\mathrm{<span\; class="notranslate">\; \&rho;</span>}}^{\mathrm{<span\; class="notranslate">\; 3</span>}}<span\; class="notranslate">\; \&CenterDot;</span>{<span\; class="notranslate">\; (</span>\frac{\mathrm{<span\; class="notranslate">\; wxya</span>}}{\mathrm{<span\; class="notranslate">\; dt</span>}}<span\; class="notranslate">\; )</span>}^{<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 7</span>}}<span\; class="notranslate">\; \&CenterDot;</span>{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&Delta;p</span>}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 4</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 14</span>}<span\; class="notranslate">\; )</span>$

in

L = measured length

Δp = pressure difference over the measuring length

Equation (13) is based on the well-known Hagen-Poiseuille law, while equation (14) is determined empirically. As far as differential pressure is concerned, both equations are monotonically increasing functions with a single point of intersection.

Thus, in a further embodiment of the invention, the measurement signal x _ζ is determined using the following relations, which are obtained by substituting the corresponding measurement signal into equations (13) and (14):

in

X _ζ1 = represents the measured value of the kinematic viscosity of the medium in the case of laminar flow

X _ζ2 = represents the measured value of the kinematic viscosity of the medium in the case of turbulent flow

x _Δp = seventh measurement signal representing differential pressure

K ₇ = seventh parameter derived from the quotient 2πD ⁴ /L according to equation (13)

K ₈ = eighth parameter derived from the quotient 0.3 ⁻⁴ D ¹⁹ /L ⁴ according to equation (14).

According to equation (15), the effective value of the measured signal x _ζ is always the smaller of the two measured values, X _{ζ1 for laminar flow and X ζ1} for turbulent flow. The first measurement is X _ζ2 .

According to equation (15), the measurement signal x _ζ depends on defined quantities generated during operation of the Coriolis mass flow/density meter, ie on the intermediate value X _m ^* and on the second measured value X _ρ . In addition, the measurement signal x _ζ depends on another defined magnitude, namely on the measurement signal x _Δp , which represents the differential pressure and is determined during operation.

In another embodiment of the present invention, in order to realize equation (15), the measurement device 144 includes the seventh sub-circuit 27 as shown in FIGS. 8 a , 8 b and the eighth sub-circuit 28 as shown in FIG. 9 .

Subcircuit 27 is used to generate two measurements representing the viscosity X _ζ1 and X _ζ2 of the medium. It comprises a third divider 271 with a dividend input for the measurement signal _xΔp and a divisor input for the intermediate value _Xm ^* . The divider 271 provides a third quotient with respect to x _Δp /X _m ^* , which is supplied to a first input of a ninth multiplier 272 . The second input of the multiplier 272 is supplied with the parameter K ₇ , so that the multiplier 272 outputs a ninth product value with respect to K ₇ ·x _Δp /X _m ^* , which corresponds to the kinematic viscosity of the medium in the case of laminar flow Measured value X _ζ1 .

The subcircuit 27 also includes a second exponentiator 273 having a signal input for the measurement signal x _Δp and a power input for a value of four. The exponentiator 273 provides a second power value with respect to (x _Δp ) ⁴ and provides it to the dividend input of the fourth divider 276 .

The subcircuit 27 also includes a third exponentiator 274 with a signal input for the intermediate value X _m ^* and a power input for a value of seven. The exponentiator 274 provides a value for the third power of (X _m ^* ) ⁷ . A fourth power multiplier 275 having a signal input for the measured value X _ρ and a power input for a value of 3 outputs a fourth power value for (X _ρ ) ³ .

The third power value (x ^* _m ) 7 is supplied to the divisor input of the fourth divider 276 , and the fourth power value (X _ρ ) ³ is supplied to the first input of the tenth multiplier 277 . The multiplier 277 has a second input for the parameter K ₈ and a third input for a fourth quotient about (x _Δp ) ⁴ /(X _m ^* ) ⁷ which is determined by the divider 276 supply. Thus, the multiplier 277 outputs a tenth product value of K ₈ ·(X _ρ ) ³ ·(x _Δp ) ⁴ /(X _m ^* ) ⁷ corresponding to a measurement representing the kinematic viscosity of the medium in the case of turbulent flow Value X _ζ2 .

The subcircuit 28 shown in Fig. 9 is used to realize the two inequalities according to equation (15). Subcircuit 28 includes a third comparator 281 having a first input for the ninth product value and a second input for the tenth product value. Comparator 281 provides a fifth binary value for K ₇ ·x _Δp /X _m ^* < K ₈ ·(X _ρ ) ³ ·(x _Δp ) ⁴ /(X _m ^* ) ⁷ if the ninth product value is less than The tenth product value, the fifth binary value is 1; otherwise, it is 0.

The fifth binary value is supplied to the second inverter 282 and to the first input of the eleventh multiplier 283 . The second input terminal of multiplier 283 is supplied with the ninth product value, thereby multiplier 283 outputs the eleventh product value, if the fifth binary value is 1, then the eleventh product value is equal to the ninth product value, if the The five-binary value is 0, and the eleventh product value is 0.

Inverter 282 provides a sixth binary value which is inverted relative to the fifth binary value and applied to a first input of twelfth multiplier 284 . The second input terminal of the multiplier 284 is supplied with the tenth product value, thereby the multiplier 284 provides the twelfth product value, if the sixth binary value is 1, then the twelfth product value is equal to the tenth product value, if the If the six binary value is 0, then the twelfth product value is 0.

The eleventh product value is provided to a first input of the fourth adder 285 and the twelfth product value is provided to a second input of the adder 285 . Since only one of the two product values is non-zero at any given time, the fourth sum produced by adder 285 is equal to the measured signal x _ζ .

Any discrepancies between the kinematic viscosity determined according to equation (15) and the actual kinematic viscosity in flow tube 11 due to eg temperature differences in the medium can be easily compensated for by appropriate temperature measurements.

The sub-circuits 21, 22, 23, 24, 25, 26, 27 and 28 are assumed to be analog computing circuits, but may also be in the form of digital computing circuits, or at least partially in digital computing circuits, by using discrete components or microprocessors. form is realized.

If the operation of subcircuits 22...28 that are actually operating in parallel is not critical in terms of time, by using multiplexers and demultiplexers in such a way that similar functions such as addition, subtraction, multiplication, Division and exponentiation are combined, that is, these functions are implemented only once in the subcircuit, and each calculated value is produced by sequentially applying the corresponding input value to the input.

Claims (15)

1. the Coriolis-type mass flowmeter/densimeter of the medium of the pipeline that is used to flow through, described Coriolis-type mass flowmeter/densimeter comprises:

-at least one has the flowtube of entrance point and endpiece, and in operating process, MEDIA FLOW is through described at least one flowtube;

-be fixed on the entrance point and endpiece of flowtube, thus the fulcrum arrangement that flowtube can be vibrated;

-in operating process, make the vibrator of flowtube vibration;

-be arranged on the entrance point of flowtube, be used at the operating process measuring vibrations, and export first measurement mechanism of first measuring-signal;

-be arranged on the endpiece of flowtube, be used at the operating process measuring vibrations, and export second measurement mechanism of second measuring-signal;

-in operating process, export the 3rd measurement mechanism of the 3rd measuring-signal of the instantaneous Reynolds coefficient of representing flow media; And

-evaluation electronic circuit is used in operating process, output

--first measured value of representation quality flow rate, first measured value is drawn by the first, the second and the 3rd measuring-signal, and

-represent second measured value of the instantaneous density of medium, this second measured value is drawn by first and second measuring-signals.

2. according to the described Coriolis-type mass flowmeter/densimeter of claim 1, wherein the evaluation electronic circuit provides the corrected value that comes from the 3rd measuring-signal.

3. according to the described Coriolis-type mass flowmeter/densimeter of claim 2, wherein the utilization of evaluation electronic circuit is by the constant corrected value of the definite laminar flow of calibration, utilize the constant corrected value of the turbulent flow of determining by calibration, and utilize and to determine according to interpolating function, interpolation corrected value between these two constant corrected values provides corrected value.

4. according to the described Coriolis-type mass flowmeter/densimeter of claim 2, wherein the evaluation electronic circuit comprises table memory, the digitizing corrected value that depends on the Reynolds coefficient is stored in this table memory, by the number storage reference address that forms according to the 3rd measuring-signal, this table memory provides corrected value.

5. according to claim 3 or 4 described Coriolis-type mass flowmeter/densimeters, wherein the evaluation electronic circuit provides the intermediate value that comes from first and second measuring-signals, and this intermediate value is represented uncorrected mass flowrate.

6. according to the described Coriolis-type mass flowmeter/densimeter of claim 5, wherein evaluation electronic circuit response intermediate value and corrected value are exported first measured value.

7. according to the described Coriolis-type mass flowmeter/densimeter of claim 6, wherein Coriolis-type mass flowmeter/densimeter comprises the 4th measurement mechanism, the kinetic viscosity of this measurement mechanism measuring media, and the 4th measuring-signal of the described kinetic viscosity of output representative.

8. according to the described Coriolis-type mass flowmeter/densimeter of claim 7, wherein the 3rd measurement mechanism responds uncorrected intermediate value and the 4th measuring-signal, exports the 3rd measuring-signal.

9. according to the described Coriolis-type mass flowmeter/densimeter of claim 7, the 5th measuring-signal of the described kinematic viscosity of the wherein kinematic viscosity of the 4th measurement mechanism measuring media, and output representative.

10. according to the described Coriolis-type mass flowmeter/densimeter of claim 9, wherein the 4th measurement mechanism responds second measured value and the 5th measuring-signal, exports the 4th measuring-signal.

11. according to the described Coriolis-type mass flowmeter/densimeter of claim 9, wherein vibrator comprises the coil that is supplied to excitation energy, according to the electric current and/or the voltage of this coil, the 4th measurement mechanism draws the 4th measuring-signal and/or the 5th measuring-signal.

12. according to the described Coriolis-type mass flowmeter/densimeter of claim 9, wherein the 4th measurement mechanism draws the 4th measuring-signal and/or the 5th measuring-signal according to the pressure reduction that records along pipeline.

13. the medium for the pipeline of flowing through produces the method for first measured value of representation quality flow rate with Coriolis-type mass flowmeter/densimeter, described Coriolis-type mass flowmeter/densimeter comprises:

-at least one has the flowtube of entrance point and endpiece, and in operating process, MEDIA FLOW is through described at least one flowtube;

-be fixed on the entrance point and endpiece of flowtube, thus the fulcrum arrangement that flowtube can be vibrated;

-in operating process, make the vibrator of flowtube vibration;

Described method comprises the steps:

-detect the vibration of flowtube, and produce first measuring-signal of representing the entrance point vibration and second measuring-signal of representing the endpiece vibration, be used to form the intermediate value of the uncorrected mass flowrate of representative;

-utilize intermediate value, and utilize the 4th measuring-signal of the kinetic viscosity of representing medium, produce the 3rd measuring-signal of the Reynolds coefficient of representing flow media; And

-utilize the corrected value that comes from the 3rd measuring-signal, proofread and correct intermediate value.

14. in accordance with the method for claim 13, wherein, draw the 4th measuring-signal according to the electric current and/or the voltage that offer the excitation energy of vibrator.

15. in accordance with the method for claim 13, wherein obtain the 4th measuring-signal according to the pressure reduction that records along pipeline.

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